MUZAFFARPUR INSTITUTE OF TECHNOLOGY,

Muzaffarpur

COURSE FILE

OF

Machine II

(031403)

Faculty Name:

Mr. R. K. Mishra

ASSOCIATE PROFESSOR, DEPARTMENT OF ELECTRICAL ENGINEERING

Content

S.No. Topic

1 Vision of department

2 Mission of department

3 PEO’s

4 PO’s

5 Course objectives and course outcomes (Co)

6 Mapping of CO’s with PO’s

7 Course syllabus and GATE syllabus

8 Time table

9 Student list

10 Lecture plans

11 Assignments

12 Tutorial sheets

13 Seasonal question paper

14 University question paper

15 Result

16 Result analysis

VISION STATEMENT OF ELECTRICAL ENGINEERING DEPARTMENT

To produce cutting edge Electrical Engineers, innovators, researchers, and entrepreneurs with

high human values to serve society, industry, nation and the world.

MISSION STATEMENT OF ELECTRICAL ENGINEERING DEPARTMENT

M1. To create state-of-the-art facilities for under-graduate, post- graduate and R&D work.

M2. To cater the needs of society with recent technologies, innovative ideas and inculcate

ethical responsibilities.

M3. To develop strong collaborative links with premier industries, institutions and the

government agencies.

Program Educational Objectives (PEOs) of Electrical Engineering Department:

PEO 1. Students will be able to engage in life-long learning and research including supportive and responsible roles on multi-disciplinary tasks.

PEO 2. Students will acquire, use and develop skills as required for effective professional and societal practices and leadership quality.

PEO 3. Students will be able to create a new dimension of innovation and entrepreneurship.

Program Outcomes (POs) based on Program Educational Objectives (PEOs) of Electrical Engineering Department:

PO 1. Students will be able to apply knowledge of applied mathematics & science in electrical engineering problems.

PO 2. Students will be able to identify, formulate and solve society and industries related problems.

PO 3. Students will be able to apply knowledge to design a system, component or process to meet desired needs within realistic constraints.

PO 4. Students will be able to conduct laboratory experiments and to critically analyze and interpret experimental data.

PO 5. Students will be able to use the recent techniques, skills, and modern tools necessary for engineering practices.

PO 6. Students will be able to understand the impact of engineering problems, solutions in a global and societal context.

PO 7. Students will be able to demonstrate professional and ethical responsibilities.

PO 8. Students will be able to apply leadership quality to work with team in the area of electrical engineering towards the solution of multi-disciplinary tasks.

PO 9. Students will be able to communicate effectively through verbally, technical writing, reports and presentation.

PO 10. Students will be able to develop confidence for self-education and ability to engage in life-long learning.

COURSE OBJECTIVE AND COURSE OUTCOMES:

Institute/college Name Muzaffarpur Institute of Technology, Muzaffarpur

Program Name B.E. Electrical (IV semester)

Course Code/course credits 031403 (4)

Course Name Machine II

Lecture/ Sessional (per week) 3/1

SEE duration 4 hours

Course Coordinator Name Mr. R. K. Mishra

Course objective:

This course is designed to achieve Excellency in the area of 3- phase alternator and 3- phase synchronous motor ,

single phase induction motor , and some special machine like as single phase synchronous motor, hysteresis

motor , stepper motor etc. All above said machine is very use full in the area of industry and social, domestic

life to fulfill the need of human and helpful the growth of society and country. The electrical machine –II covers

the fractional kilowatt and special types of machine which has versatile used in daily life. This course enhances

the knowledge and skills to faithful operation and development of machine.

Course outcomes (CO):

CO1 Students are able to understand the basic construction, mechanism of MMFs,

Electromagnetic torque production 3-phase Syn. m/c, 1-Phase IMs & special m/c.

CO2 Students are expected to learn to identify types of machine & connection mechanisms

and analyse operation & applications of 3-phase SMs and 1-phase IMs.

CO3 Students are expected to learn to analyse and evaluate 3-phase Synchronous machine

performance for both cylindrical rotor & salient rotor SMs along with 1-phase IMs.

CO4 Students are expected to be able to predict 3-phase Syn. m/c, 1-phase IMs performance

from name-plate data, and able to conduct tests to evaluate parameters of the above

machinery.

CO5 Students are expected to be able to decipher and represent machine performance

through such cryptic forms as phasor diagrams.

1: Slight (Low)

2: Moderate (Medium)

3: Substantial (High)

It there is no correlation, put

“-”

Course syllabus of Electrical machine-II

Synchronous Generator: Principle, construction and types of synchronous machines,

Methods of excitation, Armature windings, EMF equation of Alternator, Armature reaction,

testing (OC and SC test) Voltage regulation, Phasor diagram.

Two reaction : Theory Modified Phasor diagram, Power angle characteristics, Parallel

operation. Effect of change of fuel supply and excitation on alternator connected to infinite

bus , Cooling of synchronous Generator.

Synchronous Motor: Principle of operation, equivalent circuit, effect of varying field current.

V-curves, Inverted V-curves, Phasor diagram, starting of synchronous motors, hunting

application.

Single phase induction motors: Introduction, Working principle, double revolving field

theory, Equivalent circuit, Starting method and Types of single phase Induction motors,

Applications.

Special motors :Single phase synchronous motors, Two phase AC Servo Motor, single phase

series (universal) motor, stepper motor, Permanent magnet DC motor, etc, Applications.

GATE syllabus Electrical Machine-II

Operating principle of single phase induction motors; Synchronous machines: cylindrical and

salient pole machines, performance, regulation and parallel operation of generators, starting of

synchronous motor, characteristics; Types of losses and efficiency calculations of electric

machines.

Student list:

S.NO. Roll No Name

1 16EE01 NANDAN KUMAR

2 16EE02 ANJALI KUMARI

3 16EE03 KAUSTUBHA

4 16EE04 RISHABH KUMAR

5 16EE05 AMRITA KUMARI

6 16EE06 SUMIT KUMAR

7 16EE07 RITESH RAJ

8 16EE08 VIPUL MISHRA

9 16EE09 SAMEER KUMAR

10 16EE10 MD SAIFULLAH SADIQUE

11 16EE11 PREETI KUMARI

12 16EE12 KULDEEP THAKUR

13 16EE13 SHANTANU KUMAR SINGH

14 16EE14 SEEMA KUMARI

15 16EE15 PRIYAM KUMARI

16 16EE16 VANDANA BIHARI

17 16EE17 RAJNANDANI

18 16EE18 SANJAY KUMAR YADAV

19 16EE19 PRAVEEN DIVAKAR

20 16EE20 AMIT KUMAR PANDIT

21 16EE21 CHANDAN KUMAR THAKUR

22 16EE22 ALOK KUMAR

23 16EE23 DEVENDRA KUMAR

24 16EE24 ARVIND KUMAR

25 16EE25 AMITESH KUMAR

26 16EE26 VIVEK KUMAR

27 16EE27 VIKASH KUMAR RAY

28 16EE28 ROHIT KUMAR

29 16EE29 OM PRAKASH KUMAR

30 16EE30 RAVI KUMAR

31 16EE31 SANDEEP KUMAR

32 16EE32 DEO ALOK

33 16EE33 BAJRANGI KUMAR

34 16EE34 MANOJ KUMAR SONI

35 16EE35 SANJEEV KUMAR

36 16EE36 NEERAJ KUMAR

37 16EE37 SATYAM KUMAR

38 16EE38 PRASHANT GAURAV

39 16EE39 NITISH KUMAR RAJAK

40 16EE40 UJJAWAL KUMAR

41 16EE41 PRABHAT KUMAR

42 16EE42 MD HASIM JILANI

43 16EE43 SHIV CHARAN KUMAR

44 16EE44 ANISH BHARTI

45 16EE45 RAHUL KUMAR

46 16EE46 RAJEEV RANJAN PRASAD

47 16EE47 SHUBHAM KUMAR

48 16EE48 TAHIR QAMAR

49 16EE49 PRASHANT KUMAR

50 16EE50 NAMAN KUMAR

51 16EE51 KESHAV CHANDRA

52 16EE52 SWETA BHARTI

53 16EE53 PRATIK ANAND

54 16EE54 SHAGUFTA ANJUM

55 16EE55 GOLDEN KUMAR

56 16EE56 MURLI MANOHAR

57 16EE57 ARPIT ANAND

58 16EE58 AKSHAT RAJ

59 16EE59 ANJAN KUMAR

60 16EE60 SUMAN KUMAR BHARTIYA

62 16EE61 SAKET

Course Handout

1. Scope and Objectives of the Course

This course is designed to achieve Excellency in the area of 3- phase alternator and 3-

phase synchronous motor , single phase induction motor , and some special machine like

as single phase synchronous motor, hysteresis motor , stepper motor etc. All above said

machine is very use full in the area of industry and social, domestic life to fulfill the need

of human and helpful the growth of society and country. The electrical machine –II covers

the fractional kilowatt and special types of machine which has versatile used in daily life.

This course enhances the knowledge and skills to faithful operation and development of

machine.

2. Textbooks

TB1: Electrical machines by Nagrath I.J. and Kothari D.P. TMH

TB2: Electrical machinery by Fitzgerald A.E. & Kingsley: TMH

3. Reference Books

RB1: Electrical Machines by P.S. Bimbra , Khanna Publication.

RB2: Electrical machines by Samarjit Ghosh, Pearson Education Pvt. Ltd.

63 16EE62 RISHABH KUMAR

64 16EE63 SUMAN KUMAR

65 16EE64 SUNITA KUMARI

66 16EE65 NISHANT RAJ

67 16EE66 VIPIN SINGH

68 16EE67 ANKIT RAJ

69 16EE68 GUNJAN KUMAR

70 16EE69 PRATAP CHANDRA CHOUDHARY

71 17(LE)EE01 VIVEK KUMAR

72 17(LE)EE02 RITIK KUMAR

73 17(LE)EE03 ANAND RANJAN

74 17(LE)EE04 ABHISHEK KUMAR

75 17(LE)EE05 POONAM KUMARI

76 17(LE)EE06 SAURABH KUMAR JHA

77 17(LE)EE07 PARMANAND KUMAR

78 17(LE)EE08 ROHAN RAJ

79 17(LE)EE09 ANAND KUMAR

80 17(LE)EE10 MANISH

RB3: Electrical machines by purkait & bandyopadhyay, Oxford University press

Other readings and relevant websites

S.No. Link of Journals, Magazines, websites and Research Papers

1. https://www.youtube.com/watch?v=b24jORRoxEc&list=PL112E9458CF31C773

2. https://www.youtube.com/watch?v=AvvtvVUz85o

3. https://onlinecourses.nptel.ac.in

4. Course Plan

Lecture Number

Date of

Lecture Topics Web Links for video

lectures Text Book / Reference

Book / Other reading

material

Page numbers of Text Book(s)

1-9 Synchronous generator RB1, TB1, RB3 444 – 473

Synchronous generator

:Principle, construction and

types of synchronous

machines, Methods of

excitation, Armature windings,

EMF equation of Alternator,

Armature reaction,

Testing(OC and SC test)

Voltage regulation, Phasor

diagram.

https://www.youtube.c

om/watch?v=eRzVFeC

acSM https://www.youtube.c om/watch?v=tQsakkEn elc https://www.youtube.c

om/watch?v=jNyfPJTd

uC8

10-18 Two reaction RB1, TB1, RB3 475-545

Theory Modified Phasor

diagram, Power angle

characteristics, Parallel operation, Effect of change of fuel supply and excitation on alternator connected to infinite bus, Cooling of synchronous Generator

https://www.youtube.c

om/watch?v=iueIURD 4XWo https://www.youtube.c

om/watch?v=HSTVsg 5wx_4

https://www.youtube.c

om/watch?v=fR8NzZE GZSw

19-26 Synchronous Motor RB1, TB1, RB3 545-554

Principle of operation,

equivalent circuit, effect of

varying field current. V-curves,

Inverted V-curves, Phasor

diagram, starting of synchronous motors, hunting,

https://www.youtube.c

om/watch?v=80uxMIS yzxI https://www.youtube.c

om/watch?v=WKjLOg

fRnKY https://www.youtube.c

om/watch?v=SHk49rS

vVp8

27-34 Single phase induction

motors: , TB1, RB3 702-722

Introduction, Working

principle, Double revolving

field theory, Equivalent circuit,

Starting method and Types of

single phase Induction motors,

Applications.

https://www.youtube.c

om/watch?v=yL5egma

RxUM https://www.youtube.c

om/watch?v=PGs4Bs WakZE

35-42 Special motors: TB1, RB3 722-746

Single phase synchronous

motors, Two phase AC Servo

Motor, single phase series

(universal) motor, stepper

motor, Permanent magnet DC

motor, Application

https://www.youtube.c

om/watch?v=pbg_PF6

MTwY https://www.youtube.c

om/watch?v=eK12cYy

MVOg https://www.youtube.c om/watch?v=TWMai3

oirnM https://www.youtube.c

om/watch?v=P8kjv1H

wTVI

Lacture plan

SL.No. Topic Name Period

1 Synchronous Generator

Principle, construction and types of synchronous machines

1

Methods of excitation, Armature windings,

2

EMF equation of Alternator, Armature reaction

2

Testing(OC and SC test) Voltage regulation

2

Phasor diagram.

2

2 Two reaction

Theory Modified Phasor diagram, Power angle characteristics,

3

Parallel operation

2

Effect of change of fuel supply and excitation on alternator connected

to infinite bus

2

Cooling of synchronous Generator

2

3 Synchronous Motor

Principle of operation

2

equivalent circuit, effect of varying field current.

2

V-curves, Inverted V-curves

2

Phasor diagram, starting of synchronous motors

2

hunting, application

1

4 Single phase induction motors

Introduction, Working principle

1

Double revolving field theory

1

Equivalent circuit,

2

Starting method and Types of single phase Induction motors,

3

Applications

1

5 Special motors

Single phase synchronous motors,

1

Two phase AC Servo Motor

2

single phase series (universal) motor

2

stepper motor

2

Permanent magnet DC motor, Application

1

Total 42

Assignments:

Assignment I

1. Explain the excitation system of 3- phase synchronous generator.

2. Explain the equivalent circuit of 3-phase alternator & EMF method to

compute the voltage regulation.

3. Under what conditions does the voltage regulation of a synchronous

generator become negative?

4. Explain OCC & SCC in 3-phase synchronous generator.

5. Explain briefly the process of synchronizing a synchronous Generator to the

bus-bars. What conditions determine the instant of synchronization?

Assignment II

1. Explain the operation & principle of 3-phase Synchronous Motor also

described the method of starting of 3-phase Synchronous Motor.

2. Draw and explain V-curve and inverted V-curve of 3-phase Synchronous

Motor.

3. Explain Hunting in Synchronous machine. Why salient rotor synchronous

machine has more hunting than cylindrical rotor synchronous machine?

4. Explain power angle characteristics of 3-phase cylindrical rotor synchronous

machine.

5. Explain why the SCC is linear?

6. Define the Damper winding in 3 phase Synchronous machine. Explain how

Damper winding reduces the effect of hunting.

Assignment III

1. Explain why a single phase single winding induction motor not produces self

starting torque.

2. What are servomotors and list their characteristics

3. Explain Capacitor- start single phase Induction motor.

4. Explain why hysteresis motor has highest electromagnetic torque at starting.

5. Explain why 1-phase universal motor works on both AC & DC.

6. Define Stepper motor & write its applications.

TUTORIAL -I

1. Find the no- load line voltage of a star – connected 4- pole, 50 Hz alternator

from the following data:

Flux per pole= 0.12 Wb, No. of slots/ pole / phase =4

Conductor / slots= 4, Two layer winding with coil span 150 degree

electrical.

2. A 3-phase, 600 kVA alternator has rated terminal voltage of 3300 V. the

stator winding is star connected and has a resistance of 0.37 Ω/ phase and a

synchronous reactance of 4.3 Ω/ phase. Calculate the voltage regulation for

full –load at a p.f. of (i) unity (ii) 0.8 lagging.

3. A 3-phase, star-connected synchronous generator is rated at 1200 kVA, l l

kV on short-circuit a field current of 55 A gives full-load current. The OC

voltage with the same excitation is 1580 V/phase. Calculate the voltage

regulation at (a) 0.8 lagging and (b) 0.8 leading pf.

Neglect armature resistance.

4. The open- and short-circuit tests data on a 3-phase, 1 MVA, 3.6 kV, star-con

nected synchronous generator is given below:

𝐼𝑓 (A) 60 70 80 90 100 110

𝑉𝑂𝐶(line) (V) 2560 3000 3360 3600 3800 3960

𝐼𝑆𝐶 (A) 180

Find: (a) The unsaturated synchronous reactance.

(b) The adjusted synchronous reactance.

(c) The short-circuit ratio.

(d) The excitation voltage needed to give rated voltage at full-load, 0.8 lagging

pf.

TUTORIAL -II

1. A 3300 V, star-connected synchronous motor is operating at constant

terminal voltage and constant excitation. Its synchronous impedance is 0.8 +

j5 W. It operates at a power factor of 0.8 leading when drawing 800 kW

from the mains. Find its power factor when the input is increased to1200

kW, excitation remaining constant.

2. A 3300 V, star connected synchronous motor has synchronous impedance of

0.4+j0.5 Ω per phase. For an excitation e.m.f of 4000 V and motor input

power of 1000 kW at rated voltage, compute the line current and pf.

3. A 600 V, 6-pole, 3-phase, 50 Hz, star-connected synchronous motor has a

resistance and synchronous reactance of 0.4 W and 7 W respectively. It takes

a current of 15 A at upf when operating with a certain field current. With the

field current remaining constant, the load torque is increased until the motor

draws a current of 50 A. Find the torque (gross) developed and the new

power factor.

4. A 500 V, 3-phase, mesh-connected motor has an excitation emf of 600 V.

The motor synchronous impedance is (0.4 + j5) W while the windage,

friction and iron losses are 1200 W. What maximum power output can it

deliver? What is the corresponding line current, pf and motor efficiency?

TUTORIAL –III

1. Calculate the synchronizing coefficient (in kW and Nm per mechanical

degree) at fullload for a 1000 kVA, 0.8 pf (lag), 6.6 kV, 8-pole, star-

connected cylindrical rotor generator of negligible resistance and

synchronous reactance of 0.8 pu.

2. A salient-pole synchronous motor has Xd = 0.85 pu and Xq = 0.55 pu.

It is connected to bus-bars of 1.0 pu voltage, while its excitation is

adjusted to 1.2 pu. Calculate the maximum power output, the motor can

supply without loss of synchronism. Compute the minimum pu

excitation that is necessary for the machine to stay in synchronism

while supplying the full-load torque (i.e. 1.0 pu power).

3. A 440 V, 50 Hz, Y-connected salient-pole synchronous generator has a

direct-axis reactance of 0.12 W and a quadrature-axis reactance of

0.075 W per phase, the armature resistance being negligible. The

generator is supplying 1000 A at 0.8 lagging pf.

(a) Find the excitation emf, neglecting saliency and assuming Xs = Xd.

(b) Find the excitation emf accounting for saliency.

4. Figure 1.1 shows two generators supplying in parallel a load of 2.8 MW

at 0.8 pf lagging: (a) At what frequency is the system operating and

what is the load supplied by each Generator?

Fig.1.1

(b) If the load is now increased by 1 MW, what will be the new

frequency and the load sharing?

(c) In part (b) which should be the set point of G2 for the system

frequency to be 50 Hz? What would be the load sharing now?

TUTORIAL -IV

1. A 200 W, 230 V , 50 Hz , single – phase capacitor start motor has the

following constants

Main windings : R= 4.5Ω, 𝑋𝐿 =3.7 Ω

Starting winding: R= 9.5Ω, 𝑋𝐿 =3.5 Ω

Find the value of starting capacitance that will results in the maximum

starting torque.

2. A 240 V, 50 Hz, single – phase capacitor start a.c. motor is loaded such that

the slip is 6 %. The motor constants referred to the stator are:

Stator resistance =2.2 Ω; rotor resistance= 3.8 Ω

Stator reactance =3.0 Ω; rotor reactance = 2.1 Ω

Magnetizing reactance =86 Ω; Iron and friction loss= 50 W

Draw the equivalent circuit and form it, find the output power and efficiency

at the given loading.

3. For a 2-phase servomotor with a high resistance rotor, find approximate

expressions for forward and backward torques in terms of phase voltages

(differing 90° in phase) and motor speed. Assume the stator impedance and

rotor reactance to be negligible

4. A universal motor (ac-operated) has a 2-pole armature with 960 conductors.

At a certain load the motor speed is 5000 rpm and the armature current is 4.6

A; the armature terminal voltage and input are respectively 100 V and 300

W. Compute the following, assuming an armature resistance of 3.5 W.

(a) Effective armature reactance (b) Maximum value of useful flux/pole.

QUESTION BANK

Short Answer Questions :

1. Why almost all large size Synchronous machines are constructed with rotating field

system type?

2. Write down the equation for frequency of emf induced in an Alternator.

3. Why do cylindrical Alternators operate with steam turbines?

4. Which type of Synchronous generators are used in Hydro-electric plants and why?

5. What are the advantages of salient pole type construction used for Synchronous

machines?

6. Why is the stator core of Alternator laminated?

7. How does electrical degree differ from mechanical degree?

8. What is the relation between electrical degree and mechanical degree?

9. What is distributed winding?

10. Why is short pitch winding preferred over full-pitch winding ?

11. Write down the formula for distribution factor.

12. Define winding factor.

13. Why are Alternators rated in kVA and not in kW?

14. What are the causes of changes in voltage in Alternators when loaded?

15. What is meant by armature reaction in Alternators?

16. What do you mean by synchronous reactance?

17. What is meant by synchronous impedance of an Alternator?

18. What is meant by load angle of an Alternator?

19. Upon what factors does the load angle depend? An Alternator is found to have its

terminal voltage on load condition more than that on no load. What is the nature of the

load connected?

20. Define the term voltage regulation of Alternator.

21. What is the necessity for predetermination of voltage regulation?

22. Name the various methods for predetermining the voltage regulation of 3-phase

Alternator.

23. How synchronous impedance is calculated from OCC and SCC?

24. What are the advantages and disadvantages of estimating the voltage regulation of an

Alternator by EMF method?

25. Why is the synchronous impedance method of estimating voltage regulation considered as

pessimistic method?

26. What are the tests data required for predetermining the voltage regulation of an Alternator

by MMF method?

27. Why is the MMF method of estimating the voltage regulation considered as the optimistic

method?

28. State the condition to be satisfied before connecting two alternators in parallel

29. How do the synchronizing lamps indicate the correctness of phase sequence between

existing and incoming Alternators?

30. What are the advantages and disadvantages of three dark lamps method of synchronizing?

31. How Synchronoscope is used for synchronizing Alternators?

32. Why synchronous generators are to be constructed with more synchronous reactance and

negligible resistance?

33. List the factors that affect the load sharing in parallel operating generators?

34. How does the change in prime mover input affect the load sharing?

35. How does change in excitation affects the load sharing?

36. What steps are to be taken before disconnecting one Alternator from parallel operation?

37. What is meant by infinite bus-bars?

38. How does increase in excitation of the Alternator connected to infinite bus-bars affect this

operation?

39. In what respect does a 1-phase Induction motor differ from a 3-phase Induction motor?

40. What are the inherent characteristics of plain 1-phase Induction motor?

41. Name the two different theories with which principle of 1-phase induction motors are

explained.

42. State double revolving field theory.

43. Name any four types of 1-phase induction motors.

44. Why are centrifugal switches provided on many 1-phase Induction motors?

45. How the direction of a capacitor start Induction motor is be reversed?

46. Can the starting torque of a slip ring induction motor being increased?

47. What happens if the air gap flux density in an induction motor increases?

48. State the advantages of skewing?

49. What are the effects of increasing rotor resistance on starting current and starting torque?

50. What is slip of an induction motor?

51. How the magnitude of rotor emf is related to the slip in an I M?

52. How the frequency of rotor emf is related to the slip in an I M?

53. What is the normal value of slip of an I M operating at full load?

54. Why is not possible for the rotor speed of an I M to be equal to the speed of its rotating

magnetic field?

55. State the condition at which the torque developed in a 3 phase induction motor is

maximum.

56. What are the advantages of slip-ring I M over cage I M?

57. What are the losses occurring in an I M and on what factors do they depend?

58. What care should be taken at the time of construction to reduce eddy current losses in I

M?

59. Why are there not appreciable magnetic losses in the rotor core of Induction motors?

60. What is meant by synchronous watt?

61. State the characteristic features of synchronous motor.

62. In what way synchronous motor is different from other motors?

63. Name any two methods of starting a synchronous motors

64. What is the effect on speed if the load is increased on a 3 phase synchronous motor?

65. Why a synchronous motor is a constant speed motor?

66. What is the phasor relation between induced emf and terminal voltage of a 3 phase

synchronous motor?

67. At what load angle is power developed in a synchronous motor becomes its maximum

value?

68. What are V and inverted V curves of synchronous motor?

69. What happens when the field current of a synchronous motor is increased beyond the

normal value at constant input?

70. Distinguish between synchronous phase modifier and synchronous condenser 71. How

the synchronous motor can be used as s synchronous condenser?

72. What type of single phase induction motor would you use for the following applications?

73. After servicing a single phase fan it was found to run in reverse direction. What could be

the reason?

74. What will be the direction of rotation of a shaded pole single phase induction motor?

75. What is the property of a single phase single winding induction motor?

76. Which winding in a double cage induction motor has high resistance and low Inductance

Long answer Questions

1. State the requirements for paralleling of alternators.

2. A two pole,50 Hz, 3-phase, turbo alternator is excited to generate the bus-bar voltage of 11

kV on no load.The machine is star connected and the short circuit current for this

excitation is 1000A. Calculate the synchronizing power per degree of mechanical

displacement of the rotor and the corresponding synchronizing torque.

3. 3. A 3300V, 3 phase star connected alternator has a full load current of 100A on short

circuit a field current of 5A was necessary to produce full-load current. The e m f on open

circuit for the same excitation was 900V.The armature resistance was 0.8 ohm/phase.

Determine the full load voltage regulation for (i) 0.8 p f lagging (ii) 0.8 p f leading.

4. Explain the construction and principle of operation of 3-phase alternator

5. A 3-phase ,star connected, 16 pole alternaror has 192 slots with 8 conductors per slot, coil

span=160 electrical degrees, speed of alternator=375 rpm, flux per pole=55mWb.Calculate

the line and phase values of EMF generated.

6. Describe any two methods of determining the voltage regulation of 3-phase Alternator.

7. Explain the operation of single phase induction motor on the basis of double field

revolving theory.

8. Explain the operation of the types of stepper motors.

9. A 3 MVA, 50Hz, 11 kV, 3-phase star connected alternator supplies 100A at zero p f

leading. The line voltage is 12370V.When the load is removed, the line voltage is

1100V.Find the regulation at full load,0.8 pf lagging. Ra=0,4ohm/phase.

10. Bring out the characteristics of two alternators working in parallel. What is the effect of

change in excitation on load sharing?

11. Derive the equation for torque developed by an 1-phase I M. Draw the typical torque slip

curve and deduce the condition for maximum torque.

12. Write a note on Hysteresis motor.

13. Write short notes on (i)A C series motor (ii) Reluctance motor

14. How do you determine the direct axis and quadrature axis reactances of a salient pole

alternator?

15. 19. A three phase star connected alternator has direct axis synchronous reactance of 0,7p u

and quadrature axis reactance of 0,5 p u,If the generator delivers kVA at rated voltage at

full load and lagging, find the percentage regulation. Resistance drop at full load is 0.017 p

u. 16. Two alternators are connected in parallel, what happens when we (i) increase the

excitation of one machine (ii) increase the steam supply of one machine. 17. Two similar 3000kVA synchronous generators work in parallel. The governor of first

machine is such that frequency drops uniformly from 50Hz on no load to 48 Hz on full

load. The corresponding speed drop of second machine is from 50Hz to 47.5Hz.determine

the following (i) How will the two machines share a load 5000kW at full load (ii) What is

the maximum load at u p f that can be delivered without overloading either of the two

machines.

18. Explain why synchronous motor is not self starting.

19. Derive the EMF Equation of 3 phase alternator .Define distribution factor and coil span

factor?

20. Explain V-curve and inverted V-curve in 3-phase synchronous motor.

21. Explain the power angle characteristics in cylindrical synchronous machine.

22. Explain the Equivalent circuit of 3-phase alternator.

23. Briefly explain the hunting in 3-phase synchronous motor.

24. Explain the power angle characteristics in salient pole syn. Machine.

25. A 200 kVA, 480-V, 60-Hz, 4-pole, Y-Connected synchronous generator with a rated field

current of 5 A was tested and the following data was taken. a) from OC test – terminal voltage = 540 V at rated field current

b) from SC test – line current = 300A at rated field current

c) From Dc test – DC voltage of 10 V applied to two terminals, a current of 25 A was

measured. Calculate the (i) speed of rotation in r/min (ii) the generated emf and

saturated equivalent circuit parameters (armature resistance and synchronous

reactance)